Many methods for the precision transfer and handling of fluids are known and used in a variety of commercial and industrial applications. The biotechnology and biopharmaceutical industries are particularly relevant examples of industries requiring ultra-pure fluid handling and transfer techniques. Current biotechnological screening and manufacturing methods also require high throughput to efficiently conduct screening of compound libraries, synthesis of screening component, and the like.
Various current fluid transfer methods require contacting the fluid with a transfer device, e.g., a pipette, a pin, a needle or the like. Such contact methods dramatically increase the likelihood of contamination. Many biotechnology procedures, e.g., polymerase chain reaction (PCR), are extremely sensitive and can tolerate essentially no contamination. Accordingly, non-contact liquid transfer techniques are desirable.
Acoustic liquid dispensing is an example of a suitable non-contact dispensing technique that can eject droplets without contaminating the source liquid. Typically, such ejectors require focussing acoustic energy at or near the free surface of the source fluid to be ejected. To this end, it is desirable to control the free surface of a source liquid during droplet ejection because otherwise droplet ejection can be less accurate, and even fail.
Various methods and structures have been developed to affect the free surface of a source liquid pool in acoustic printing/ejection. For example, U.S. Pat. Nos. 4,719,476; 4,719,480 and 5,142,307 disclose techniques for spatially stabilizing capillary surface waves in liquid ink printing and similar applications.
U.S. Pat. Nos. 5,216,451; 5,428,381 and 5,686,945 disclose capping structures having openings for use with ink printing applications. U.S. Pat. No. 5,028,937 discloses an acoustic ink printer comprising a pool of ink having a free surface in intimate contact with the inner face of a perforated membrane and U.S. Pat. No. 5,808,636 discloses a method for reduction of droplet misdirectionality in acoustic ink printing. The above mentioned patents however do not include the features and benefits of the present invention as will described further below. Accordingly, an improved apparatus and method useful in controlling the free surface of a source liquid in a source liquid container is desired.